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This global commission report aims to redefine how obesity is diagnosed. The report suggests that looking solely at Body Mass Index (BMI) is not sufficient because it’s not a direct measure of fat, or its distribution. The report suggests other measurements of body (e.g. amount of body fat, waist-to-hip ratio) are required.
The report also suggests marking a difference between obesity that hasn’t affected how the organs function (termed in the report as pre-clinical obesity) and obesity that does (clinical obesity).
The authors argue that this would allow for more personalised care, using different strategies for people in different positions, while also stressing the importance of not assigning blame or increasing stigma.
Prof Carel le Roux, Professor of Metabolic Medicine, University College Dublin (UCD), said:
“This consensus of world experts has achieved a level playing field to allow all stakeholders to have a common language and understanding of the disease of obesity. We can now start a serious conversation about how we can work together and move away from the idea of weight loss to the idea of health gain to address both clinical obesity and preclinical obesity.”
Dr Alexandra Cremona, Associate Professor of Human Nutrition and Dietetics, University of Limerick, said:
“This study is significant because it redefines obesity as a complex, chronic systemic illness, moving beyond the limitations of a BMI-centric model to focus on the functional impairments and health impacts caused by excess adiposity. By introducing the concepts of “preclinical” and “clinical” obesity, it enhances diagnostic precision, enabling individualized care that considers both risk and active disease states. This reframing also addresses weight stigma by emphasizing the biological and systemic factors underlying obesity, rather than attributing it solely to personal choices, thus promoting equitable healthcare access. Moreover, the study provides a clear distinction between health and illness in obesity, offering actionable pathways for healthcare policy, early intervention strategies, and targeted research into disease mechanisms. If adopted, this innovative framework has the potential to refine current models of obesity care, improve patient outcomes, and shift public health approaches, making it a pivotal contribution to the field.
The study’s strengths lie in its global expertise, with contributions from 58 international experts and endorsements from 76 organizations, ensuring its applicability across diverse populations. Its comprehensive framework moves beyond BMI, integrating direct fat measurement (e.g., DEXA scans), anthropometric criteria (e.g., waist circumference, waist-to-hip ratio), and functional assessments (e.g., organ dysfunction and limitations in daily activities) to enhance diagnostic precision. By focusing on organ dysfunction and quality of life, it highlights the real-world impact of obesity, making the recommendations clinically relevant. The rigorous Delphi consensus methodology ensures evidence-based, well-validated findings, while the inclusion of individuals with lived experience adds an empathetic, patient-centred perspective. These features together mark a significant step forward in advancing obesity care.
Certain limitations warrant attention: implementing advanced diagnostic methods like DEXA scans may be resource-intensive, particularly in low-resource settings. The study also lacks longitudinal data on outcomes and cost-effectiveness, which are essential for assessing the impact of its recommendations in real-world contexts. Additionally, the distinction between “preclinical” and “clinical” obesity may complicate practical diagnosis, especially for general practitioners. While the criteria emphasize physical health impacts, mental health aspects of obesity may be underrepresented, limiting a holistic understanding of the condition. As with any newly published recommendations, challenges may be faced in integration and adoption into existing systems. However, these limitations are not insurmountable and can be addressed through further research to evaluate outcomes, refine criteria, and develop scalable solutions tailored to diverse healthcare settings.
The findings are robust and innovative, marking a potential paradigm shift in obesity care. The distinction between preclinical and clinical obesity is particularly valuable as it acknowledges the spectrum of obesity-related health impacts, from risk factors to manifest disease. The emphasis on functional impairments rather than solely body size aligns more closely with patients’ lived experiences and the complexities of chronic diseases.
The integration of the Lancet Commission’s framework into Ireland’s recently adapted obesity guidelines offers an opportunity to enhance and elevate the current approach. By refining diagnostic criteria and emphasizing the distinction between preclinical and clinical obesity, this framework could bring greater precision to care and prevention strategies. However, successful implementation will require further research to bridge gaps and adapt the recommendations to Ireland’s specific context. The framework’s focus on reducing weight bias and stigma is particularly commendable, aligning with the need to remove barriers to effective obesity management and foster equitable healthcare practices.
The Lancet Commission’s redefinition of obesity as “preclinical” and “clinical” closely parallels the Edmonton Obesity Staging System (EOSS), particularly its staging of obesity as progressing from minimal risk (Stage 0 and 1) to more severe health impacts (Stages 2–4). However, the Lancet framework attempts to differentiate itself by explicitly framing “preclinical obesity” as a risk state (excess adiposity with preserved organ function) and “clinical obesity” as a distinct chronic disease characterized by organ dysfunction or significant functional limitations. While this distinction may seem similar to EOSS’s progression of stages, the Lancet places stronger emphasis on recognizing obesity as an independent disease entity rather than solely a risk factor for comorbidities. This reframing offers potential to influence public health policies and clinical approaches by shifting focus to diagnosing and managing obesity itself, irrespective of associated conditions. Nonetheless, the practical differences between the two frameworks may feel minimal, and whether this redefinition significantly advances clinical care will depend on its implementation and adoption.”
Dr Laura McGowan, Senior Lecturer in Nutrition and Behaviour Change, Queen’s University Belfast, said:
“This Lancet Commission represents an important step forward in the field of obesity and the care for those living with obesity.
It advances scientific agreement across a broad range of experts on what constitutes clinical obesity, and how we can consider this as a clinical condition in its own right, and more than just a risk factor for other conditions, like type 2 diabetes and cardiovascular disease.
The research is robust in its methods and a strength is that it included the views and opinions of those living with obesity.
It is particularly relevant for those living in Northern Ireland, as at present, patients here don’t have access to NHS-supported specialist obesity management services, including new wave medications like the GLP-1’s and bariatric surgery. Defining clinical obesity and making the diagnostic criteria clear may help this to become better resourced within the NHS in NI, which is urgently needed.”
‘Definition and diagnostic criteria of clinical obesity’ was published in The Lancet Diabetes and Endocrinology at 23:30 Irish time Tuesday 14th January 2025.
DOI: https://doi.org/10.1016/S2213-8587(24)00316-4
Declarations of interest
Prof le Roux is an author on the report.